﻿using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Data;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace Stardance.IEnumerable
{
    public static class IEnumerableEx
    {
        /// <summary>
        /// 将普通集合转为通知属性集合
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="coll"></param>
        /// <returns></returns>
        public static ObservableCollection<T> ToObservableCollection<T>(this IEnumerable<T> coll)
        {
            var oc = new ObservableCollection<T>();
            foreach(var item in coll)
            {
                oc.Add(item);
            }
            return oc;
        }

        /// <summary>
        /// 集合转换为DataTable
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="varlist"></param>
        /// <returns></returns>
        public static DataTable ToDataTable<T>(this IEnumerable<T> varlist)
        {
            DataTable dtReturn = new DataTable();
            // column names 
            PropertyInfo[] oProps = null;
            if (varlist == null) return dtReturn;
            foreach (T rec in varlist)
            {
                // Use reflection to get property names, to create table, Only first time, others will follow 
                if (oProps == null)
                {
                    oProps = ((Type)rec.GetType()).GetProperties();
                    foreach (PropertyInfo pi in oProps)
                    {
                        Type colType = pi.PropertyType;

                        if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition() == typeof(Nullable<>)))
                        {
                            colType = colType.GetGenericArguments()[0];
                        }

                        dtReturn.Columns.Add(new DataColumn(pi.Name, colType));
                    }
                }
                DataRow dr = dtReturn.NewRow();
                foreach (PropertyInfo pi in oProps)
                {
                    dr[pi.Name] = pi.GetValue(rec, null) == null ? DBNull.Value : pi.GetValue
                    (rec, null);
                }
                dtReturn.Rows.Add(dr);
            }
            return dtReturn;
        }



    }
}
